The current invention relates to the field of electronic circuits. More particularly, the current invention relates most directly to improvements in networked computer environments and has particular applications to the transmission of information between digital devices over a communications medium. The invention also is concerned with the interface between a network adaptor and its host operating system in order to improve network performance and reduce network operation burden on a host processor. The invention concerns in some details a network adaptor driver, which generally consists of program code running on a host's CPU which controls or interfaces with aspects of adaptor operation.
The present invention has applications to the field of computer systems and networks. A very wide variety of types of computer systems and networks exist, each having variations in particular implementations. The present invention will be described with reference to particular types of systems for clarity but this should not be taken to limit the invention, and it will be apparent to those of skill in the art that the invention has applications in many different types of computer systems. The invention therefore should not be seen as limited except as specifically herein provided.
Digital computer networks have become ubiquitous in academic, industry, and office environments. A number of different aspects of computer networks are discussed in co-assigned pending U.S. applications Ser. Nos. 08/313,674; 08/542,157; 08/506,533; and 08/329,714 each of which are incorporated herein by reference.
Networking Devices Standards
This specification presumes familiarity with the general concepts, protocols, and devices currently used in LAN networking and WAN internetworking applications such as, for example, the IEEE 802 and ISO 8802 protocol suites and other series of documents released by the Internet Engineering Task Force that are publicly available and discussed in more detail in the above-referenced patent applications and will not be fully discussed here.
FIG. 1
FIG. 1 illustrates a local area network (LAN) 40 of a type that might be used today in a moderate-sized office or academic environment and as an example for discussion purposes of one type of network in which the present invention may be effectively employed. LANs are arrangements of various hardware and software elements that operate together to allow a number of digital devices to exchange data within the LAN and also may include internet connections to external wide area networks (WANs) such as WANs 82 and 84. Typical modern LANs such as 40 are comprised of one to many LAN intermediate systems (ISs) such as ISs 60-62 and 67 that are responsible for data transmission throughout the LAN and a number of end systems (ESs) such as ESs 50a-d, 51a-c, and 52a-g, that represent the end user equipment. The ESs may be familiar end-user data processing equipment such as personal computers, workstations, and printers and additionally may be digital devices such as digital telephones or real-time video displays. Different types of ESs can operate together on the same LAN. In one type of LAN, LAN ISs 60-61 are referred to as bridges and WAN ISs 64 and 66 are referred to as routers, and IS 67 is referred to as a repeater, however many different LAN configurations are possible, and the invention is not limited in application to the network shown in FIG. 1.
The LAN shown in FIG. 1 has segments 70a-e, 71a-e, and 72a-e, and 73a. A segment is generally a single interconnected medium, such as a length of contiguous wire, optical fiber, or coaxial cable or a particular frequency band. A segment may connect just two devices, such as segment 70a, or a segment such as 72d may connect a number of devices using a carrier sense multiple access/collision detect (CSMA/CD) protocol or other multiple access protocol such as a token bus or token ring. A signal transmitted on a single segment, such as 72d, is simultaneously heard by all of the ESs and ISs connected to that segment.
LANs also may contain a number of repeaters, which is one configuration possible shown for device 67. A repeater generally repeats out of each of its ports all data received on any one port, such that the network behavior perceived by ESs such as 50d-f is identical to the behavior they would perceive if they were wired on the same segment such as 52d-g. Repeaters configured in a star topology, such as 67, are also referred to as hubs. In alternative network topologies, device 67 could be a bridge as described below.
Drivers, Adaptors, and LAN Topology
Each of the ISs and ESs in FIG. 1 includes one or more adaptors and a set of drivers. An adaptor generally includes circuitry and connectors for communication over a segment and translates data from the digital form used by the computer circuitry in the IS or ES into a form that may be transmitted over the segment, e.g., electrical signals, optical signals, radio waves, etc. An ES such as 50b will generally have one adaptor for connecting to its single segment. A LAN IS such as 61 will have five adaptors, one for each segment to which it is connected. A driver is a set of instructions resident on a device that allows the device to accomplish various tasks as defined by different network protocols. Drivers are generally software programs stored on the ISs or ESs in a manner that allows the drivers to be modified without modifying the IS or ES hardware.
LANs may vary in the topology of the interconnections among devices. In the context of a communication network, the term “topology” refers to the way in which the stations attached to the network are interconnected. Common topologies for LANs are bus, tree, ring, and star. LANs may also have a hybrid topology made up of a mixture of these. The overall LAN pictured in FIG. 1 has essentially a tree topology, but incorporating one segment, 72d, having a bus topology, and incorporating one segment 70d having a star topology. A ring topology is not shown in FIG. 1, but it will be understood that the present invention may be used in conjunction with LANs having a ring topology.
Other Network Devices
The LAN ISs in LAN 40 include bridge/switches 60-63. Bridges are understood in the art to be a type of computer optimized for very fast data communication between two or more segments. A bridge according to the prior art generally makes no changes to the packets it receives on one segment before transmitting them on another segment. Bridges are not necessary for operation of a LAN and, in fact, in prior art systems bridges are generally invisible to the ESs to which they are connected and sometimes to other bridges and routers.
FIG. 2 is a diagram illustrating a server 500t transmitting to three receivers 500a, 500b and 500c via a network 84 according to one embodiment of the present invention.
Packets
In a LAN such as 40, data is generally transmitted between ESs as independent packets, with each packet containing a header having at least a destination address specifying an ultimate destination and generally also having a source address and other transmission information such as transmission priority. ESs generally listen continuously to the destination addresses of all packets that are transmitted on their segments, but only fully receive a packet when its destination address matches the ES's address and when the ES is interested in receiving the information contained in that packet.
FIG. 3 depicts an example of a packet as it may be transmitted to or from router 64 on LAN segment 73a. The example shown is essentially an Ethernet packet, having an Ethernet header 202 and a 48-bit Ethernet address (such as 00:85:8C:13:AA) 204, and an Ethernet trailer 230. Within the Ethernet packet 200 is contained, or encapsulated, an IP packet, represented by IP header 212, containing a 32 bit IP address 214 (such as 199.22.120.33). Packet 200 contains a data payload 220 which holds the data the user is interested in receiving or holds a control message used for configuring the network. Many other types and configurations of packets are known in the networking art and will be developed in the future.
Layers
An additional background concept important to understanding network communications is the concept of layered network protocols. Modern communication standards, such as the TCP/IP Suite and the IEEE 802 standards, organize the tasks necessary for data communication into layers. At different layers, data is viewed and organized differently, different protocols are followed, and different physical devices handle the data traffic. FIG. 4 illustrates one example of a layered network standard having a number of layers, which we will refer to herein as the Physical Layer, the Data Link Layer, the Routing Layer, the Transport Layer and the Application Layer. These layers correspond roughly to the layers as defined within the TCP/IP Suite. (The 802 standard has a different organizational structure for the layers and uses somewhat different names and numbering conventions.)
An important ideal in layered standards is the ideal of layer independence. A layered protocol suite specifies standard interfaces between layers such that, in theory, a device and protocol operating at one layer can coexist with any number of different protocols operating at higher or lower layers, so long as the standard interfaces between layers are followed.
Adaptor to Host Interface
Another aspect of networks is the interface between the network and the host operating system or processors that transmit data via the network. Some types of network protocols may require a large amount of attention from a host processor. This can be undesirable where a hosts activity on the network impinges on the hosts processor's ability to perform other host functions such as running user applications. Adaptors may also differ in their ability to buffer network traffic. Some adaptors rely on the host to buffer most network traffic and do not include a large amount of buffer memory on the adaptor itself.
Increasing Traffic Capacity of Some Network Devices Create a Need for New Solutions to Improve Network Performance
In recent years, the amount of data users wish to transmit over a network has increased dramatically. This increase has placed an increasingly heavy burdens on all parts of the network. A number of existing networks include a mixture of components or segments, some capable of operating at a maximal speed of the network and others operating at slower speeds.
What is needed is an improved network and components allowing for greater utilization of network resources in a distributed network environment and with techniques for preventing bottlenecks in slower components in a distributed network from unduly degrading overall network performance or preventing full utilization of faster components.